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(t)Bu(3) PPd(Ph)Br (1)-catalyzed Suzuki-Miyaura coupling polymerization of 2-(4-hexyl-5-iodo-2-thienyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2) was investigated. Monomer 2 was polymerized with 1 at 0 °C in the presence of CsF and 18-crown-6 in THF containing a small amount of water to yield P3HT with a narrow molecular weight distribution and almost perfect head-to-tail regioregularity. The M(n) values increased up to 11,400 g · mol(-1) in proportion to the feed ratio of 2 to 1. The MALDI-TOF mass spectra showed that P3HT with moderate molecular weight uniformly had a phenyl group at one end and a hydrogen atom at the other, indicating involvement of a catalyst-transfer mechanism. Successive 1-catalyzed polymerization of fluorene monomer 3 and then 2 yielded a well-defined block copolymer of polyfluorene and P3HT., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

ABSTRACT To synthesize ladder-type polyamides by construction of two amide bonds successively, 2,5-diaminoterephthalic acid derivatives bearing anthranilic acid ester and isatoic anhydride moieties were synthesized and their polymerization was investigated. Polymerization of the methyl ester monomer proceeded in the presence of lithium hexamethyldisilazide (LiHMDS) as a base in tetrahydrofuran (THF). However, mass spectroscopic analysis of the product suggested that not only the bis(trimethylsilyl)amide anion of LiHMDS but also the methoxide anion eliminated at the second amide-linkage formation reaction decomposed the isatoic anhydride unit of the growing oligomer by nucleophilic attack to disturb the polymerization. To reduce the nucleophilicity of the eliminated anion, methyl ester of the monomer was changed to phenyl ester and its polymerization was studied. The reaction conditions were optimized, and the best result was obtained when the polymerization was conducted in the presence of 1.0 equivalent of LiHMDS without additives in THF at 50 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2365-2372 [ABSTRACT FROM AUTHOR]

ABSTRACT Application of chain-growth condensation polymerization (CGCP) to obtain well-defined polybenzoxazole (PBO) was examined. CGCP of both phenyl 3-{(2-methoxyethoxy)methoxy (MEM-oxy)}-4-(octylamino)benzoate ( 1b) ( para-substituted monomer) and phenyl 4-MEM-oxy-3-(octylamino)benzoate ( 3b) ( meta-substituted monomer) was examined in the presence of metal disilazide base and phenyl 4-nitro- or methylbenzoate 2 as an initiator. Polymerization of the latter monomer, but not the former, afforded polymer with controlled molecular weight based on the feed ratio of monomer to initiator and with a narrow molecular weight distribution. Accordingly, monomer 3c, in which the octyl group on the amino nitrogen of 3b was replaced with a 4-(octyloxy)benzyl (OOB) group, was polymerized in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS), phenyl 4-methylbenzoate ( 2b), and LiCl in THF at 0 °C to yield poly 3c with well-defined molecular weight ( Mn = 4520-9080) and low polydispersity ( Mw/ Mn ≤ 1.11). Treatment of poly 3c with trifluoroacetic acid simultaneously removed the MEM and OOB groups, affording poly( o-hydroxyamide) (poly 4) without scission of the amide linkages. Cyclodehydration of poly 4 proceeded at 350 °C to yield PBO (poly 5), which was insoluble in organic solvents and acids. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1730-1736 [ABSTRACT FROM AUTHOR]

Condensation reaction of poly(ethylene glycol) (PEG) with a carboxyl group at one chain end and hyperbranched polyamide (HBPA) with a hydroxyl group at the focal point was performed in the presence of condensation agent at ambient temperature, yielding PEG ‐ b ‐ HBPAs with defined molecular weight and very narrow molecular weight distribution. PEG ‐ b ‐ HBPA formed micelles in water. [ABSTRACT FROM AUTHOR]

Condensation polymerization of 5-aminoisophthalic acid methyl ester 1 bearing a N-tri(ethylene glycol) methyl ester (TEG) chain as an AB2 monomer was conducted and the properties of the resulting hyperbranched polyamides (HBPA) were investigated. When the polymerization of 1 was carried out with N-methyl core initiator 2b at various feed ratios of 1 to 2b ([1]0/[2b]0) in the presence of LiHMDS and LiCl at -10 °C, the Mn values of the obtained HBPA increased in proportion to the [1]0/[2b]0 ratio from 7 to 46 (Mn = 3810-18600), retaining a narrow molecular weight distribution (Mw/Mn = 1.11-1.19). The HBPA was soluble in water, and a 0.25 wt.-% aqueous solution of the HBPA exhibited a lower critical solution temperature (LCST). The cloud point was 21-23 °C, which is about 30 °C lower than that of the corresponding poly(m-benzamide) with the N-TEG unit. [ABSTRACT FROM AUTHOR]

Ni-catalyzed Kumada–Tamao coupling polymerizationof 5-bromo-3-chloromagnesio-2-(2-(2-methoxyethoxy)ethoxy)pyridine(1) was investigated. Monomer 1, which wasobtained quantitatively by treatment of the corresponding bromoiodopyridine 3with 1.0 equiv of iPrMgCl at0 °C, was polymerized with Ni(dppp)Cl2(dppp = 1,3-bis(diphenylphospino)propane))in the presence of 2.0 equiv of LiCl in THF at room temperature toyield poly(2-(2-(2-methoxyethoxy)ethoxy)pyridine-3,5-diyl) (m-PMEEOPy) with narrow polydispersity. The Mnvalue was controlled by the feed ratio of the monomerprecursor 3to Ni(dppp)Cl2. MALDI-TOF massspectra showed that m-PMEEOPy uniformly had a bromineatom at one end and a hydrogen atom at the other. Both end groupscould be converted to aryl groups by addition of an excess of arylmagnesium chloride to the reaction mixture after completion of thepolymerization. These results indicate that the polymerization of 1with Ni(dppp)Cl2involves the intramolecularcatalyst-transfer polymerization mechanism. [ABSTRACT FROM AUTHOR]

The article presents a study on the chain-growth condensation polymerization that results to well-defined polymers and π-conjugated polymers. It notes that differences in the substituent effects between the monomer and polymer lead to the activation of the polymer end group and change polymerization mechanism to chain-growth process. Moreover, chain-growth condensation polymerization can produce architectures with well-defined polymers and the development of π-conjugated polymers.

This article covers the synthesis and self-assembly of several polymer architectures containing condensation polymers with low polydispersities by chain-growth condensation polymerization utilizing substituent effects. Well-defined AB, ABA, BAB, ABC type block copolymers, star polymers, star block copolymers and miktoarm star copolymers containing aromatic polyamide or aromatic polyether as a segment were synthesized by 1) sequential addition of monomers, 2) a polymer coupling reaction, 3) a macroinitiator method with modification of polymer end group, and 4) macroinitiator method with an orthogonal initiator. Furthermore, the polymers self-assembled in a unique way. [ABSTRACT FROM AUTHOR]

Abstract: The historical development of research on the living polymerization process in polycondensation is reviewed. Classical polycondensation is a step-growth process, but a living polymerization polycondensation must proceed by a chain-growth rather than a step growth mechanism. Early work demonstrated that some polycondensations do not obey Flory''s statistical treatment: for example, high molecular weight polymer may be obtained, even at low conversion. This means that a chain-growth mechanism must be involved, with or without a step-growth mechanism. Recent years have seen dramatic development in understanding of polycondensations that proceed only by chain-growth (chain-growth polycondensation). Several possible mechanisms are: (1) activation of the polymer end group by changed substituent effects between the monomer and the polymer, as with aromatic polyamides, polyesters, polyethers, poly(ether sulfone)s and poly(ether ketone)s; (2) activation of the polymer end group by transfer to it of the catalyst, as with polythiophenes; (3) transfer of the reactive species, derived from the initiator, to the polymer end group, as with polymethylenes and polyphosphazenes; and (4) phase-transfer polymerization in a biphase composed of a monomer storage phase and a polymerization phase, as with aliphatic polyesters. These chain-growth polycondensations have been applied to the synthesis of condensation polymers with various architectures: block copolymers, star polymers, graft copolymers, etc. [Copyright &y& Elsevier]

We studied the mechanism of the chain-growth polymerization of 2-bromo-5-chloromagnesio-3-hexylthiophene (1) with Ni(dppp)Cl2 [dppp = 1 ,3-bis(diphenylphosphino)propane], in which head-to-tail poly(3-hexylthiophene) (HT-P3HT) with a low polydispersity is obtained and the Mn is controlled by the feed ratio of the monomer to the Ni catalyst. Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectra showed that the HT-P3HT uniformly had a hydrogen atom at one end of each molecule and a bromine atom at the other. The reaction of the polymer with aryl Grignard reagent gave HT-P3HT with aryl groups at both ends, which indicates that the H-end was derived from the propagating Ni complex. The degree of polymerization and the absolute molecular weight of the polymer could be evaluated from the 1H NMR spectra of the Ar/Ar-ended HT-P3HT, and it was found that one Ni catalyst molecule forms one polymer chain. Furthermore, by reaction of 1 with 50 mol % Ni(dppp)Cl2, the chain initiator was found to be a bithiophene-Ni complex, formed by a coupling reaction of 1 followed by insertion of the Ni(0) catalyst into the C-Br bond of the dimer. On the basis of these results, we propose that this chain-growth polymerization involves the coupling reaction of 1 with the polymer via the Ni catalyst, which is transferred intramolecularly to the terminal C-Br bond of the elongated molecule. We call this mechanism "catalyst- transfer polycondensa tiorP. [ABSTRACT FROM AUTHOR]

In this review article, polycondensation that proceeds in a chain-growth polymerization manner ("chain-growth polycondensation") for well-defined condensation polymers are described. Our approach to chain-growth polycondensation is (1) activation of polymer end group by substituent effects changed between monomer and polymer and (2) phase-transfer polymerization in biphase composed of monomer store phase and polymerization phase. In the approach (1), a variety of condensation polymers such as aromatic polyamides, aromatic polyesters, aromatic polyethers, poly(ether sulfone), and polythiophene with defined molecular weights and low polydispersities were obtained. Their polycondensations had all of the characteristics of living polymerization: a linear correlation between molecular weights and monomer conversion maintaining low polydispersities, and control over molecular weights by the feed ratio of monomer to initiator. Taking advantage of the nature of living polymerization in this polycondensation, we synthesized diblock copolymers of different kinds of aromatic polyamides and of aromatic polyamide and conventional polymers such as poly(ethylene glycol), polystyrene, and poly(tetrahydrofuran), as well as triblock copolymers and star polymers containing aromatic polyamide units. Some copolymers were arranged in a supramolecular self-assembly. In the approach (2), the polycondensation of solid monomer dispersed in organic solvent with a phase transfer catalyst (PTC) was carried out, where solid monomer did not react with each other, and the monomer transferred to organic solvent with PTC reacted with an initiator and the polymer end group selectively inorganic solvent, to yield well-defined polyesters. [ABSTRACT FROM AUTHOR]

Polymerization of diphenylacetylene and trans-stilbene monomers bearing 4-alkylamino and 4'-phenoxy- or 4'-alkoxycarbonyl groups was carried out with an initiator in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide. Chain-growth polymerization afforded corresponding polyamides, whereas stepgrowth polymerization resulted in the formation of cyclic oligoamides. [ABSTRACT FROM AUTHOR]

This article cites a study, which states that not only para-substituted AB-type aromatic monomers but also meta-substituted ones undergo chain-growth polycondensation by virtue of different inductive effects between monomer and polymer. This I effect- assisted polycondensation should enable us to extend the synthesis of well-defined condensation polymers from pat-a-substituted aromatic polymers to a variety of meta-substituted ones, which possess higher solubility. Furthermore, this polymerization method should be applicable to chain-growth polycondensation of even aliphatic monomers, such as amino acid and lactic acid derivatives.

The polycondensation of phenyl 4-(octylamino)benzoate (1) proceeded in a chain-polymerization manner to yield aromatic polyamides with low polydispersities (Mw/Mn ≤ 1.1) even under normal conditions for step-growth polycondensation, in which initiator was not added. On the basis of the results of the polycondesations of 1 with initiator models, this self-initiated chain-growth polycondensation involves the formation of the dieter of 1, which initiates the chain-growth polymerization faster than step-growth polymerization. [ABSTRACT FROM AUTHOR]

Successive catalyst-transfer condensation polymerization of a Grignard-type phenylene monomer and then a thiophene monomer with a Ni catalyst yields well-defined block copolymers of poly(p-phenylene) and polythiophene, but the reverse order of polymerization results in polymers with broad molecular weight distribution. [ABSTRACT FROM AUTHOR]

The article examines the catalyst transfer of conductive polymers with controlled molecular weight and low polydispersity. In one study, the polycondensation of a Grignard thiophene monomer with Ni-Cl2 as catalysts would proceed into a chain-growth polymerization mechanism. A monomer addition experiment was conducted to determine the chain-growth nature of the polymerization.